Transamination techniques can be used to prepare amine compounds and mixtures of amine compounds from lower molecular weight amines. Transamination can provide acyclic and/or cyclic amine products.
GB Patent No. 1508460 discloses the transamination of ethylenediamine (EDA). U.S. Pat. Nos. 4,568,746 and 7,053,247 also discloses the transamination of EDA. GB Patent No. 155127 discloses the transamination of 1,3-diaminopropane (1,3-DAP). U.S. Pat. No. 6,465,601 discloses the preparation of mixed amines by the transamination of a substituted phenolic compound (Mannish base) with another amine. The mixed amines are useful as accelerators for curable epoxy and polyurethane systems. US 2008/0132725 A1 discloses the preparation of bis(3-aminopropyl)amine (dipropylenetriamine, DPTA) by the continuous reaction of 1,3-propylenediamine in the presence of a heterogeneous catalyst in a reaction column. None of these publications disclose the preparation of higher molecular weight polyamines. In fact, they generally teach processes wherein such materials are not made or if made can be redecomposed to the dimers and trimers under the reaction conditions employed.
Although transamination has proved itself as a viable way to manufacture amines on an industrial scale, several challenges remain. First, the ability to customize product mixtures for desired end uses can be limited. Additionally, some processes produce mixtures whose contents promote the formation of cyclic polyamines and discourage the formation of higher molecular weight, acyclic polyamines. While cyclic species are desired for some applications, higher molecular weight, acyclic species are also desired for many other applications. For example, higher molecular weight, acyclic linear species are useful in a variety of applications such as paper manufacture, water treatment conditioning, plating, bath agents, dispersing agents, asphalt additives, corrosion inhibitors, epoxy curing agents, fuel and lubricant additives, mineral processing aids, wood treating, etc. While there are a number of processes that form higher molecular weight polyamines, they generally form only a small quantity of these amines and/or produce undesirable byproducts. It would be desirable to have a process that could minimize the formation of cyclic amines and encourage the formation of higher molecular weight amines from readily available starting materials.
U.S. Patent Publication 2009/0018040 discloses that higher molecular weight polyamines are desirable for some purposes. It describes a method for forming higher molecular weight polyethyleneamines in which lower molecular weight ethyleneamines are coupled through the use of difunctional linking groups such as epihalohydrins, maleates, α-halogenated acids, and malonates. The use of such linking groups to build molecular weight is not cost effective and can introduce other functional groups, which are not desired.
Higher molecular weight polyamines, such as higher molecular weight ethyleneamines (i.e., amines containing 4 or more N atoms) may be produced from ethylene dichloride and ammonia. This process, sometimes referred to as the EDC process, produces a complex mixture of various linear, cyclic, and branched products with a number-average molecular weight of 250-300 g/mole. This process produces a significant amount of cyclic and branched amines.